Acute Management Overview

Agent Identification

Nerve agents (NAs) are the most toxic of the known chemical warfare agents. They are chemically similar to organophosphate pesticides (OPs) and exert their biological effects by inhibiting acetylcholinesterase enzymes.

Nerve agents can cause loss of consciousness and convulsions within seconds and death from respiratory failure within minutes of exposure.

Volatile Nerve Agents (vapor)

Nerve agent vapor is readily absorbed by inhalation and ocular contact and produces rapid local and systemic effects.

G-type agents are clear colorless and tasteless liquids that are soluble in water and most organic solvents.

GB is odorless and is the most volatile nerve agent; however, it evaporates at about the same rate as water. GA has a slightly fruity odor and GD has a slight camphor-like odor (these are not reliable).

Low Volatility Nerve Agents (liquid)

Liquid nerve agent is readily absorbed through the skin; however, effects may be delayed for several minutes to up to 18 hours.

VX is a clear, amber-colored, odorless, oily liquid. It is soluble in water as well as in all other solvents. It is the least volatile nerve agent.

Responders should obtain assistance in identifying the chemical(s) from container shapes, placards, labels, shipping papers, and analytical tests. General information on these identification technicques is located in Emergency Response Guidebook.

Patients who are conscious and have full muscular control will need minimal care.

Patients with a history of possible exposure to vapor only (with no possibility of liquid exposure) who have no signs of exposure by the time they reach the medical facility have not been exposed (because these effects occur within seconds to minutes after exposure). They can be discharged.

Delayed Effects from skin exposure to liquid nerve agent may not develop for up to 18 hours following exposure.

Patients who have inhalation exposure and who complain of chest pain, chest tightness, or cough should be observed and examined periodically for 6 to 12 hours to detect delayed-onset bronchitis, pneumonia, pulmonary edema, or respiratory failure.

Patients exposed to nerve agent vapor that have only miosis and/or mild rhinorrhea when they reach the medical facility do not need to be admitted. All other patients who have had exposure to nerve agent should be hospitalized and observed closely.

Route of Exposure

Inhalation - nerve agents are readily absorbed from the respiratory tract. Runny nose and tightness in the throat or chest begin within seconds to minutes after exposure. Nerve agent vapors are heavier than air. Odor does not provide adequate warning of detection.

Skin/Eye Contact - nerve agent liquids are readily absorbed from the skin and eyes. Vapors are not absorbed through the skin except at very high concentrations. Ocular effects may result from both direct contact and systemic absorption. The nature and timing of symptoms following dermal contact with liquid nerve agents depend on exposure dose; effects may be delayed for several hours.

Ingestion - ingestion of nerve agents is expected to be relatively rare compared to inhalation exposure or skin contact; however, they are readily absorbed from the GI tract and are highly toxic.

Clinical Signs and Symptoms

Nerve agents are potent acetylcholinesterase inhibitors causing the same signs and symptoms regardless of the exposure route. However, the initial effects depend on the dose and route of exposure.

Children are much more vulnerable than adults to nerve agent toxicity.

Hot Zone

If contaminated patients arrive at the Emergency Department, they must be decontaminated before being allowed to enter the facility. Decontamination can only take place inside the hospital if there is a decontamination facility with negative air pressure and floor drains to contain the contamination.

Rescuers should be trained and appropriately attired before entering the Hot Zone. If the proper equipment is not available, or if rescuers have not been trained in its use, call for assistance in accordance with local Emergency Operational Guides (EOG). Sources of such assistance should be obtained from a local HAZMAT teams, mutual aid partners, the closest metropolitan strike system (MMRS) and the U.S. Soldier and Biological Chemical Command (SBCCOM)-Edgewood Research Development and Engineering Center. SBCCOM may be contacted (from 7:00 AM - 4:30 PM EST call 410-671-4411 and from 4:30PM - 7:00AM EST call 410-278-5201), ask for the Staff Duty Officer.

Hot Zone

Agent Identification

Nerve agents are the most toxic of the known chemical warfare agents. They are chemically similar to organophosphate pesticides and exert their biological effects by inhibiting acetylcholinesterase enzymes.

Nerve agents can cause loss of consciousness and convulsions within seconds and death from respiratory failure within minutes of exposure.

Volatile Nerve Agents (vapor)

Nerve agent vapor is readily absorbed by inhalation and ocular contact and produces rapid local and systemic effects.

G-type agents are clear colorless and tasteless liquids that are miscible in water and most organic solvents.

GB is odorless and is the most volatile nerve agent; however, it evaporates at about the same rate as water. GA has a slightly fruity odor and GD has a slight camphor-like odor.

Low Volatility Nerve Agents (liquid)

Liquid nerve agent is readily absorbed through the skin; however, effects may be delayed for several minutes to up to 18 hours.

VX is a clear, amber-colored, odorless, oily liquid. It is miscible with water and soluble in all solvents. It is the least volatile nerve agent.

Responders should obtain assistance in identifying the chemical(s) from container shapes, placards, labels, shipping papers, and analytical tests. General information on these identification technicques is located in Emergency Response Guidebook.

Rescuer Protection

Nerve Agent is a highly toxic systemic poison that is easily absorbed by inhalation and through the skin. Victims exposed only to nerve agent vapor do not pose secondary contamination risks to rescuers, but do not attempt resuscitation without a barrier. Victims whose clothing or skin is contaminated with liquid nerve agent can secondarily contaminate response personnel by direct contact or through off-gassing vapor. Avoid dermal contact with nerve agent contaminated victims or with gastric contents of victims who may have ingested nerve agent-containing materials.

PPE required: level B-C

Most likely B-C PPEs will be adequate. Levels As may be required if the hospital is close to the site of exposure and/or there is concern for vapor exposure (bring in HAZMAT for Level A PPEs).

Skin Protection: Chemical-protective clothing is recommended because both nerve agent vapor (high exposure doses) and liquid can be absorbed through the skin to produce systemic toxicity.

Level A - protective clothing is the highest level of protection. Level A includes a Self Contained Breathing Apparatus (SCBA) with a fully encapsulating vapor tight suit with gloves and booties attached to the suit (tanks last from 1/2 hour to 1 hour).

Level B - requires the use of SCBA but has lesser skin protection. Level Bs are chemical resistant suits that are designed for splashes of liquids, but not for gas or vapor hazards. A young soldier can last about 2 hours on a hot day with an external air hose.

Level C is similar to B with the exception of the type of respiratory protection. The SCBA is replaced with an Air Purifying Respirator.

Level D protective clothing is utilized when there are no respiratory hazards and no major skin hazard considerations. Level D for hospital personnel includes scrubs, safety glasses, shoe covers, and possibly a face shield.

Triage

Chemical casualty triage is based on walking feasibility, respiratory status, age, and additional conventional injuries. The triage officer must know the natural course of a given injury, the medical resources immediately available, the current and likely casualty flow, and the medical evacuation capabilities.

For the victim esposed to nerve agent who presents with severe multisystem symptoms, antidotes and supportive care can be lifesaving if initiated immediately.

General Principles of Triage for Chemical Exposures

Severe casualty triaged as immediate if assisted breathing is required.

Blast injuries or other trauma, where there is question whether there is chemical exposure, victims must be tagged as immediate in most cases. Blast victim's evidence delayed effects such as ARDS, etc.

Mild/moderate casualty: self/buddy aid, triaged as delayed or minimal and release is based on strict follow up and instructions.

If there are chemical exposure situations which may cause delayed but serious signs and symptoms, then over-triage is considered appropriate to the proper facilities that can observe and manage any delayed onset symptoms.

Expectant categories in multi-casualty events are those victims who have experienced a cardiac arrest, respiratory arrest, or continued seizures immediately. Resources should not be expended on these casualties if there are large numbers of casualties requiring care and transport with minimal or scant resources available.

In a given category prioritize a child, pregnant woman over a non-pregnant adult.

Patients who are conscious and have full muscular control will need minimal care.

Patients with a history of possible exposure to vapor only (with no possibility of liquid exposure) who have no signs of exposure by the time they reach the medical facility have not been exposed (because these effects occur within seconds to minutes after exposure). They can be discharged.

Delayed Effects from skin exposure to liquid nerve agent may not develop for up to 18 hours following exposure.

Patients who have inhalation exposure and who complain of chest pain, chest tightness, or cough should be observed and examined periodically for 6 to 12 hours to detect delayed-onset bronchitis, pneumonia, pulmonary edema, or respiratory failure.

Patients exposed to nerve agent vapor that have only miosis and/or mild rhinorrhea when they reach the medical facility do not need to be admitted. All other patients who have had exposure to nerve agent should be hospitalized and observed closely.

ABC Reminders

Speed is critical. If the victim is symptomatic, immediately institute emergency life support measures including the use nerve agent specific antidotes. Quickly ensure that the victim has a patent airway and is ventilating well. Assist ventilation with a bag-valve-mask device equipped with a canister or air filter if necessary Maintain adequate circulation. Antidote (atropine) administration may be required to enable ventilation. Stabilize the cervical spine with a decontaminable collar and a backboard if trauma is suspected. Direct pressure should be applied to control heavy bleeding, if present.

Route of Exposure

Inhalation - nerve agents are readily absorbed from the respiratory tract. Runny nose and tightness in the throat or chest begin within seconds to minutes after exposure. Nerve agent vapors are heavier than air. Odor does not provide adequate warning of detection.

Skin/Eye Contact - nerve agent liquids are readily absorbed from the skin and eyes. Vapors are not absorbed through the skin except at very high concentrations. Ocular effects may result from both direct contact and systemic absorption. The nature and timing of symptoms following dermal contact with liquid nerve agents depend on exposure dose; effects may be delayed for several hours.

Ingestion - ingestion of nerve agents is expected to be relatively rare compared to inhalation exposure or skin contact; however, they are readily absorbed from the GI tract and are highly toxic.

Clinical Signs and Symptoms

The onset of action with inhaled vapor can be almost instantaneous causing local and systemic effects. Liquid which is readily absorbed thru the skin can cause system effects in minutes and up to 18 hours later.

Cardiovascular: Potentially up to three phases in variable length - transient tachycardia/with or without hypertension (minutes) followed by bradycardia and hypotension. The final phase starts hours to days after exposure with QT prolongation and a tendency toward malignant dysrhythmias. In one organophosphate toxicity study, 42 % had cardiac arrhythmias with torsades de pointe occurring in 37 % of the cases.

Gastrointestinal: Abdominal pain, nausea & vomiting (N&V), diarrhea are common manifestations of any exposure. It may be the first systemic effects of skin exposure. If GI symptoms occur within one hour of dermal contamination severe intoxication is present.

Ocular: Symptoms may occur from local effects secondary to vapor exposure or as a manifestation of systemic absorption. Pinpoint pupils, eye pain, conjunctivitis, and increased tearing are common (with systemic absorption pinpoint pupils may not occur immediately).

Treatment in the Hot Zone

Consult with a medical toxicologist or a poison center at the national toll-free number 1-800-222-1222 for further guidance on appropriate antidote dosing.Currently two atropine/pralidoxime autoinjector formulations exist:

Duodote - a single autoinjector contains approximately 600 mg of pralidoxime and 2 mg of atropine

In general treatment of severe nerve agent poisoning requires lower total doses of atropine than required for treatment of organophosphorous compounds

In severe cases of nerve agent toxicity following vapor exposure (i.e. apneic and unconscious) it may take up to 15 mg of atropine to restore consciousness and breathing. Typically atropine has not been required for more than 3 hours to treat the life threatening effects. Non-life threatening effects such as nausea and vomiting have required atropine for 6-36 hours.

Organophosphate ingestions have required hundreds of mgs a day of atropine

Mild effects:

Miosis alone ( no respiratory symptoms)- No antidotes. However, if eye/head pain or N&V (in the absence of other systemic signs suggesting a liquid exposure) are severe, use atropine ophthalmic drops.

These include localized swelling, muscle fasciculations, nausea and vomiting, weakness, shortness of breath. Utilize autoinjectors, if available. May use a 600 mg 2PAM Cl autoinjector in an infant as small as 12 kg.

If resistance to ventilation is significant , requiring repeat dosing in less than 5 minutes utilize the higher doses and increase frequency depicted in the severe effects section below

Treat vomiting and diarrhea from a liquid exposure in a similar way.

Regular IM atropine dosing may take 20-25 minutes to have a therapeutic effect (vs. 8 minutes with an autoinjector).

May repeat pralidoxime - up to a total of 45 mg/kg during the first hour.

May repeat pralidoxime - up to 45 mg/kg 1 hour after initial treatment.

Severe Effects - Initial Dosing:

These include unconsciousness, convulsions, apnea, flaccid paralysis and requiring assisted ventilation (severe respiratory distress). I.V. atropine has produced ventricular fibrillation in hypoxic animals with nerve agent poisoning. Therefore it is recommended that hypoxia be corrected prior to atropine administration. However atropine should not be withheld due to fears of this complication. It would be preferable to utilize an atropine autoinjector for the first dose in the hypoxic nerve agent exposed patient.

Diazepam or midazolam should be given to all patients having seizure activity, unconsciousness, diffuse muscle twitching, and if >1 organ is involved. The military gives diazepam as part of initial therapy for any seriously ill NA exposed patients. Utilized early, atropine may function as an anticonvulsant. The benzodiazepines are the most effective seizure medication for nerve agent toxicity.

If available, IV administration of diazepam is the preferable route for treatment of seizures.

Victim Removal

If victims can walk, lead them out of the Hot Zone to the Decontamination Zone. Victims who are unable to walk may be removed on backboards or gurneys; if these are not available, carefully carry or drag victims to safety. Should there be a large number of casualties, and if decontamination resources permit, separate decontamination corridors should be established for ambulatory and non-ambulatory victims.

Consider appropriate management of chemically contaminated children, such as measures to reduce separation anxiety if a child is separated from a parent or other adult.

Decontamination Zone

Rapid decontamination is critical to prevent further absorption by the patient and to prevent exposure to others. Because of the high toxicity, rapid absorption, and volatility; it is unlikely that a patient brought to a medical facility will have nerve agent on the skin. However, some nerve agent may remain in the hair or clothing and should be decontaminated if not previously done.

Decontamination Zone

Rescuer Protection

Personnel should continue to wear the same level of protection as required in the Hot Zone.

If exposure levels are determined to be safe, decontamination may be conducted by personnel wearing a lower level of protection than that worn in the Hot Zone. However, do not attempt resuscitation without a barrier.

ABC Reminders

Speed is critical. If the victim is symptomatic, immediately institute emergency life support measures including the use nerve agent specific antidotes. Treatment should be given simultaneously with decontamination procedures. Quickly ensure that the victim has a patent airway and is ventilating well. Assist ventilation with a bag-valve-mask device equipped with a canister or air filter, if necessary. Maintain adequate circulation. Atropine administration may be required to enable ventilation. Stabilize the cervical spine with a decontaminable collar and a backboard if trauma is suspected. Direct pressure should be applied to control heavy bleeding, if present.

Children and the elderly are at increased risk for hypothermia - provide warm showers, blankets.

Privacy must be considered, if possible.

The decontamination system should be designed for use in children of all ages, by parentless children, the non-ambulatory child, the child with special needs, and also allow families to stay together.

Use step-by-step, child-friendly instructions that explain to the children and parents what they need to do, why they are doing it, and what to expect.

Take into consideration that infants when wet are slippery and will need a way to get them through the decontamination process - i.e. plastic buckets, car seats, stretchers...

Designate a holding area and provide staff to support and supervise the children.

Recommended age-appropriate staffing ratios for untended children:

1 adult to 4 infants

1 adult to 10 preschool children

1 adult to 20 school-age children

Washing Instructions

If there will be significant delay to decontamination, have the victims rinse off with water exposed skin surfaces and disrobe (disposable clothing kits should be available).

Remove all clothing (at least down to their undergarments) and place the clothing in a labeled durable 6-mil polyethylene bag (removal of clothing, at least to the undergarment level will reduce victim's contamination by 85 %).

If exposure to liquid agent is suspected, cut and remove all clothing and wash skin immediately with soap and water.

If exposure to vapor only is certain, remove outer clothing and wash exposed skin with soap and water.

The eyes must be decontaminated within minutes of exposure to liquid nerve agent to limit injury. Flush the eyes immediately with water for about 5 to 10 minutes by tilting the head to the side, pulling eyelids apart with fingers, and pouring water slowly into eyes. There is no need to flush the eyes following exposure to nerve agent vapor. Remove contact lenses if easily removable without additional trauma to the eye.

If clothes have been exposed to contamination, then extreme care must be taken when undressing to avoid transferring chemical agents to the skin - i.e. any clothing that has to be pulled over your head should be cut off instead of being pulled over your head.

Scraping with a wooden stick, i.e. a tongue depressor or popsicle stick, can remove bulk agent.

Cover all open wounds with plastic wrap prior to performing head to toe decontamination (particular attention should be made to open wounds because cyanide is readily absorbed through abraded skin).

Flush the exposed skin and hair with plain water for 2 to 3 minutes then wash twice with mild soap. Rinse thoroughly with water. Be careful not to break the patient/victim's skin during the decontamination process.

Caution - many people shower as they do it at home rather than conducting a rapid decontamination of their bodies. Too aggressive scrubbing can lead to further damage to skin and open wounds.

Irrigate exposed or irritated eyes with plain water or saline for 5 minutes. Continue eye irrigation during other basic care or transport. Remove contact lenses if easily removable without additional trauma to the eye.

Utilizing large amounts of water by itself is very effective (limit pressure in infants).

If water supplies are limited, and showers are not available an alternative form of decontamination is to use absorbent powders such as flour, talcum powder, or Fuller's earth (0.5% sodium hypochlorite solution is contraindicated).

Sodium hypochlorite is not recommended for use in infants and young children.

Certification of decontamination is accomplished by any of the following: processing through the decontamination facility; M8, M9 tape; M256A1 ticket; or by the Chemical Agent Monitor (CAM).

If still contaminated, repeat shower procedure.

In cases of ingestion, do not induce emesis. If the victim is alert, asymptomatic, and has a gag reflex, administer slurry of activated charcoal (administer at 1 gm/kg, usual adult dose 60-90 g, child dose 25-50 g). A soda can and a straw may be of assistance when offering charcoal to a child (consider nasogastric tube - if possible contact ED prior to use of NG tube in infants and children [risk vs. benefit of inducing emesis with NG tube placement]).

Decontamination of First Responder

Begin washing PPE of the first responder using soap and water solution and a soft brush. Always move in a downward motion (from head to toe). Make sure to get into all areas, especially folds in the clothing. Wash and rinse (using cold or warm water) until the contaminant is thoroughly removed.

Reactive Skin Decontamination Lotion (RSDL) - designed to be carried by First Responders and warfighters, this lotion was found to be highly effective in removing and or neutralizing groups of chemical warfare agents. RSDL performed significantly better than the predicate device against the agents tested. The foam applicator immediately removes the CW agent off the skin and the CW Agent is chemically changed to a non-toxic form. Once the CW Agent is decontaminated, RSDL leaves a non-toxic residue that can be rinsed off when operational conditions allow.

Decontamination of Infants and Children

Decontamination of Children (HHS/AHRQ) provides a step-by-step decontamination demonstration in real time, and trains clinicians about the nuances of treating infants and children, who require special attention during decontamination.

Treatment Area

Treatment Area

Treatment Area Re-Triage

Following decontamination, the patient should be reassessed; noting changes in triage category (if any), the need for or the modification of supportive therapy as well as the initiation or continuation of nerve agent specific antidotes.

Patients exposed to vapor who have miosis and rhinorrhea will need no care unless:

(a) they have eye or head pain or nausea and vomiting; under these circumstances topical atropine or homatropine in the eye should relieve the symptoms and the patient can be discharged within an hour or so; or

(b) the rhinorrhea is very severe; under these circumstances, atropine IM (2 mg in adults and 0.05 mg/kg in children) should relieve this and the patient can be discharged in an hour or so.

Topical atropine and homatropine should not be used routinely for miosis because they cause visual impairment for about 24 hours.

Advanced Treatment

Severe Exposure

Review Airway, Breathing, Circulation, Disability, and Exposure. Place patient in the Left Lateral Position, preferably with head lower than the feet, to reduce the risk of aspirating stomach contents. Provide high flow oxygen, if available. Intubate the patient if their airway or breathing is compromised. Treat complicating injuries.

Obtain IV access and give 1-3 mg, (0.02 mg/kg for infants) of atropine†* as a bolus, depending on severity. Set up an infusion of 0.9 % normal saline; aim to keep the systolic BP >80 mmHg and urine output >0.5 ml/kg/hr.

Atropine should not be given IV if at all possible, in a hypoxic patient exposed to nerve agent or organophosphates. IV Atropine has regularly produced ventricular fibrillation in test animals in these clinical situations. Give at least the initial dose IM via autoinjector. Regular IM dosing may take 20-25 minutes to have a therapeutic effect.

Record pulse rate, blood pressure, pupil size, presence of sweat, and auscultatory findings at time of first atropine dose.

Do not give the loading dose too rapidly as it causes vomiting, tachycardia, and diastolic hypertension.

Five minutes after giving atropine, check pulse, blood pressure, pupil size, sweat and chest sounds. If there has been no improvement, give double the original dose of atropine.

Continue to review every 5 mins - give doubling doses of atropine if there has been no response. Once parameters have begun to improve, there is no need to double each dose.

Give atropine boluses until the heart rate is > 80 bpm, the systolic BP >80 mmHg, (See PEDIATRIC VITAL SIGN) values and the chest is clear (while appreciating that atropine will not clear focal areas of aspiration). Sweating usually also stops. A tachycardia is not a contraindication to atropine since it can be caused by many factors. The pupils will commonly dilate; however, this is not a useful endpoint for initial atropinization because there is a delay to maximum effect. However, very dilated pupils are commonly an indicator of atropine toxicity. Test visual acuity.

Once the patient is stable, start an infusion of atropine giving per hour around 10-20 % of the dose used to initially atropinize the patient. Observe the patient often to see if too much or too little is being given. If too little, cholinergic features will reappear after a while. If too much, patients will become agitated and pyrexial and develop absent bowel sounds and urinary retention. If this occurs, stop the infusion and wait 30-60 minutes for these features to settle before starting again at a lower infusion rate.

Continue the oxime infusion until atropine has not been required for 12-24 hrs and the patient extubated.

Treatment of seizures - diazepam†* or midazolam‡* should be given to all patients having seizure activity, unconsciousness, diffuse muscle twitching, and if >1 organ is involved. The military gives diazepam as part of initial therapy for any seriously ill NA exposed patients. Utilized early, atropine may function as an anticonvulsant. The benzodiazepines are the most effective seizure medication for nerve agent toxicity. Once seizures are under control, may repeat doses of diazepam or midazolam Q2-4 h PRN. If one benzodiazepine doesn't work initially, try the other. Consider continuous infusion of midazolam, ketamine/anesthesia for non-responsive status. EEG monitoring on a PRN basis.

Review flexor neck strength regularly in conscious patients by asking them to lift their head off the bed and keep it there when pressure is applied to their forehead. Any sign of weakness is a sign that the patient is at risk of developing peripheral respiratory failure (intermediate syndrome - seen occasionally with organophosphate toxicity/ not associated with nerve agent). The tidal volume should be checked in such patients every 4 hrs. Values less than 5 ml/kg are an indication for intubation and ventilation.

Treat agitation by reviewing the dose of atropine being administered and giving adequate sedation with benzodiazepines. An antipsychotic, such as haloperidol, can be used but may be less effective for alcohol withdrawal, a frequent co-morbidity in self-poisoned patients. Physical restraint of agitated patients in warm conditions risks severe hyperthermia - this is exacerbated greatly by atropine which inhibits normal thermoregulatory responses, including sweating. Adequate sedation is therefore important.

Fluids, electrolytes, nutrition - children have lower reserves of fluid and are more vulnerable to GI loses, correct acidosis, nursing mothers should pump and discard breast milk until cleared medically.

Eye care - treat eye pain, miosis (atropine will not reverse miosis).

Monitor frequently for recurring cholinergic crises due to leaching of fat soluble OPs from fat stores. Such crises can occur for several days to weeks post-ingestion of some OPs. Patients with recurring cholinergic features will need reloading with atropine.

While this has not been demonstrated with nerve agent exposure, monitor for the potential development of intermediate syndrome (IMS). This is a syndrome of muscular paralysis occurring in conscious patients typically 24-96 hours (it may occur earlier or later) following ingestion of certain organophosphate agents (following the acute cholinergic syndrome which was treated with atropine). Muscle weakness affects predominantly the proximal limb muscles and those supplied by the cranial nerves. IMS is often associated with respiratory failure.

Ingestion Exposure - Do not induce emesis because of the risk of pulmonary aspiration of gastric contents which may result from abrupt respiratory arrest, seizures, or vomiting. Consideration of decontamination should only be considered after the patient has been stabilized and treated with oxygen, atropine, and an oxime. If the patient is alert and charcoal has not been given previously, administer slurry of activated charcoal (questionable efficacy). If the patient's condition is evaluated within two hours after ingestion of a substantial amount of OP and the patient is fully alert or intubated, consider gastric lavage (some Chinese studies recommend multiple lavages) [Gastric contents should be considered potentially hazardous by skin contact or inhalation and should be quickly isolated].

Laboratory Tests

Cholinesterase assays

A diagnosis of OP/NA poisoning should be ideally confirmed with an assay to measure BuChE activity in the plasma. However the lack of an assay or delay of access to an assay should not delay treatment.

Some OPs inhibit BuChE more effectively than they inhibit AChE. Since BuChE activity does not relate to the severity of the poisoning, BuChE inhibition cannot be used to assess severity. It can however be used as a sensitive marker of 1) exposure to most OPs or other ChE-inhibiting compound and 2) when the OP has been eliminated from the body.

Red cell AChE is a good marker of synaptic function and atropine requirements in OP/NA poisoned patients and, therefore, a good marker of severity. Severe symptoms of toxicity are usually present when more than 70 % of RBC cholinesterase is inhibited. However, there is no correlation between cholinesterase activity and severity of topical signs and symptoms (e.g., miosis, rhinorrhea, dyspnea). A major problem with AChE assays is that the interaction between OP, AChE, and oximes continues to occur if the sample is left at room temperature for even a few minutes. To get reliable results, it is essential to stop the reaction immediately when the blood sample is taken from the patient, by cooling and diluting it. Otherwise differences in time to sample cooling of only a few minutes for repeated sampling will cause marked variation and make interpretation difficult.

Disposition and Follow-up

Patients who have severe exposure should be evaluated for persistent CNS signs and symptoms. Refer patients with neuropsychiatric sequelae appropriately as these are likely secondary to nerve agent. Patients should be advised to avoid organophosphate insecticide exposure until sequential RBC cholinesterase activity (measured at weekly to monthly intervals) has stabilized in the normal range, a process that may take 3 to 4 months after severe poisoning.

Follow-up Instructions

Call your doctor or the Emergency Department if you develop any unusual signs or symptoms within the next 24 hours, especially:

dizziness, loss of coordination, loss of memory

coughing, wheezing, or shortness of breath

nausea, vomiting, cramps, or diarrhea

muscle weakness or twitching

blurred vision

No follow-up appointment is necessary unless you develop any of the symptoms listed above.

Call for an appointment with Dr. _____________ in the practice of ___________________.
When you call for your appointment, please say that you were treated in the Emergency Department at ____________ Hospital by _______________ and were advised to be seen again in ______ days.

Return to the Emergency Department/Clinic on __________ (date) at ____________ AM/PM for a follow-up examination.

Do not perform vigorous physical activities for 1 to 2 days.

You may resume everyday activities including driving and operating machinery.

Do not return to work for _______ days.

You may return to work on a limited basis. See instructions below.

Avoid exposure to cigarette smoke for 72 hours; smoke may worsen the condition of your lungs.

Avoid drinking alcoholic beverages for at least 24 hours; alcohol may worsen injury to your stomach or have other effects.

Avoid taking the following medications: ________________________________

You may continue taking the following medication(s) that your doctor(s) prescribed for you:
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________

Provide the Emergency Department with the name and the number of your primary care physician so that the ED can send him or her a record of your emergency department visit.

You or your physician can get more information on the chemical by contacting: ____________________________ or ________________________, or by checking out the following Internet Web sites: ________________________; ___________________________.